In motor vehicles, batteries are used for supplying electrical energy. The batteries supply energy to start an internal combustion engine of the motor vehicle. Batteries also provide loads which have to be operated when the internal combustion engine is in a stationary state and additional electrical energy for loads when the internal combustion engine is operated. The batteries are charged by a generator driven by the internal combustion engine.
In order to save fuel, it is known to charge the batteries by controlling the generator during vehicle braking to recapture the kinetic energy implemented during braking. Various methods have been developed for this which are intended to increase use of the battery and recovery of energy. In particular, battery monitoring systems (BMS) have been developed which determine the current state of charge (SOC), i.e. the proportion of the currently maximum storable charge which is actually stored at a particular time and the current charging capacity (or state of health, SOH), i.e. the proportion of a setpoint capacity of the battery that can be used at a particular time, so as to use this capacity to control the charging of the battery.
In many cases, the integral of current over time is used to determine the current state of charge SOC. The available charging capacity SOH drops in the course of a battery life. Methods for determining the state of charge SOC and the charging capacity SOH within the scope of a battery monitoring system are known, for example, from German Patent Application Nos. DE 10 2006 001 201 B4 titled “Procedure for controlling a battery charge procedure,” DE 10 2007 050 346 A1 titled “Capacity-related state variable validation method for electrical energy storage i.e. battery, of motor vehicle, involves concluding plausibility of capacity-related state variable of storage depending on evaluation parameter,” and DE 10 2008 034 461 A1 titled “Procedure and device for the determination of the operating condition of an automotive battery.”
German Patent No. DE 41 24 496 A1 titled “Brake Assembly for Motor Vehicles with Electric Drive,” which is not of the generic type, discloses that a brake system, provided for motor vehicles with an electric drive, is embodied in the form of a multi-circuit compound brake system which comprises friction brakes which act on the driven or on the non-driven wheels and an electro-regenerative brake system which is coupled directly or indirectly to the brake pedal and acts on the driven wheels.
It is desirable, however, to have a different method of managing battery recharging.